Welcome to the forum! If you can call it that, its more like a playground full of kids with ADHD.
I got my WFP system from Pure Freedom, which are fairly reasonable with pricing, they kitted and fitted out my van, for much cheaper than some of the big names you hear on the forum. All of which do a good job, but some are just overkill if you are starting out and dont have the cashflow. Birmingham, there is a firm called Xline Systems based some where in your area i think, they were my 2nd choice as there systems look really good. Maybe give them a call and ask for some advice, or get them to put a price together for you for a full package.
Dont bother with trad, i did for 2 years and looking back it was a waste of time, WFP all the way, longterm much more benefits all round. If you dont have any cashflow though, then start trad only on bungalows, then get yourself a trolley system and start doing upstairs with that, trad downstairs, until you get enough money saved away for a van mount.
Ultimately though, it will be cheaper longterm to just invest in a van mount straight away, as you will make so much more per day/week/month.
Buy yourself a TDS Meter online, to test if your water is hard or soft, this will help determine what type of filtration setup you need. Once again though, if you phone any of the suppliers, ask to speak to somebody that can help out a "newbie" and give you advice on everything you need to get started.
Good luck!